The Epstein-Barr virus (EBV) is highly penetrant in AIDS-associated non-Hodgkin's lymphomas where it is a key driver of the tumor phenotype. While EBV latency genes are critical for facilitating the tumor phenotype, the switch from latency to the lytic cycle is a critical aspect of a successful EBV infection program. As a result, the mechanisms driving this switch have been topics of active investigation over the years. Although EBV reactivation can be achieved in tissue culture through stimulation of the B-cell receptor (with anti-Ig) or the TGF-beta receptor (with ectopic TGF-beta), it is uncertain how common such events are in EBV-infected lymphocytes in vivo (work from David Thorley-Lawson's lab). The overarching hypothesis of this application is that EBV has evolved with a sensing mechanism for latently infected B-cells to detect when they encounter an epithelial cell environment. This model proposes that environmental cues from the oral/tonsil epithelium (in the late stages of the germinal center reaction, for example) trigger reactivation in B-cells, thereby facilitating the B-cell to epithelial cell viral transfer that is a fundamental first step n oral epithelial plaque formation and host- to-host transmission.